1. Field of the Invention
This invention relates to the fields of semiconductor, optical component and electro-optic component processing and manufacturing, and in particular, to a method and apparatus for in-situ monitoring and controlling deposited film thicknesses in real-time.
2. Description of Related Art
In semiconductor manufacturing, the fabrication processes that are used to date must be very accurately controlled due to the constant increase in integration density of the resultant integrated circuit. One of the important process steps in semiconductor processing, as well as in other types of device processing, is the deposition of films, such as those formed into interconnect lines, bus structures, Schottky barriers, ohmic contacts or other device structures.
Appropriate thickness of the deposited metal film is imperative to the performance of the resultant device. The thickness of the film must be precisely controlled because variations in thickness may affect the electrical properties of the layers and adjacent device patterns, particularly in the interconnections between different layers of microelectronic devices. For example, if too thin a metal film is deposited, an interconnect line formed from that film may be unacceptably resistive or may have a greater likelihood of becoming an open circuit either during subsequent processing steps or during the normal operation of the device. A thick metal film is also undesirable as the film deposition process takes too long and the film thickness may be in excess of the tolerances of later processing steps. Accordingly, it is desirable to maintain film thicknesses near their optimal levels.
In so stating, tools used for such semiconductor manufacture processing have becoming more and more complex over the years. For example, typical processing tools may include a plurality of chambers, whereby each chamber runs a number of varying processing steps. A wafer is sequentially introduced within each of the plurality of chambers and processed sequentially therein, generally under the control of a computer. Typically, the deposition monitoring techniques within such chambers are often performed using repetitive techniques and generally require test wafers. The film thickness is generally measured on one or more of the test wafers, after the film has been deposited thereon, to determine if the film thickness is near an optimal level and if the process is within normal operating parameters. If the measured film thickness and parameters are not within the desired tolerances, the process parameters are adjusted and more test wafers are measured to assure optimal film thickness and process compliance. These processes have a number of disadvantages including, for example, being costly as one or more test wafers must be utilized, time consuming as the film thickness must be measured after the film is deposited thereon, unreliable from wafer-to-wafer and inefficient compared to current deposition monitoring techniques.
Accordingly, as variations of certain process variables cannot be accurately predicted over the course of many process runs using the above systems, new methods for tool and process characterization such as gas analysis, in-situ monitoring and the like, are now of common use in the semiconductor industry. Further, external film thickness metrology, located outside of the wafer processing tool, typically is used as a film thickness monitor. However, as it is advantageous to monitor the progress of critical wafer processing steps to ensure that the steps are properly completed, it is desirable to utilize in-situ process monitoring systems. In-situ monitoring systems improve both process monitoring as well as control of the processing steps based on such process monitoring.
In-situ monitoring systems have been developed to monitor and control the deposition of a film onto a wafer surface, as well as for film removal systems such as those for detecting an endpoint of a process. The endpoint determination is used to monitor the progress of the process and/or to control the process, such as by automatically terminating the specific processing operation being monitored. In film removal systems and processes, it must be accurately determined when enough of the film has been removed; i.e., to detect the endpoint of the removal operation. If an etch step exceeds the predetermined endpoint, the substrate, insulating layer and/or resultant circuit pattern may be damaged. As such, these systems typically rely on in-situ measurements to determine the progressive depth of the etch process as these systems provide greater control of the etch process and improve uniformity over a batch of processed wafers.
There has been some success in the art of developing in-situ film thickness deposition and etch depth measuring systems that utilize optical emission spectroscopy to monitor light emissions from the plasma as the etch process progresses. Such a system may monitor the optical emission intensity of the plasma in a narrow band as well as a wide band and generates signals indicative of the spectral intensity of the plasma by collecting the optical emissions using an optical fiber. When the signals diverge, a termination signal is generated thereby terminating the etch process. However, such systems typically require a separate light source, the measurement is done on spots on the wafer, and in the case where multiple spots need to be measured at least part of the measurement equipment needs to be duplicated for such measurement as well as the computation time increasing. As such, these methods and technologies for film thickness determinations are slow, costly, inefficient, unreliable and negatively impact production yield. Other techniques include the use of laser interferometry, beamsplitters and diffraction gratings to measure the phase shift of a laser beam reflected from two closely spaced surfaces. For example, the phase shift between a first beam reflected off the mask pattern and the beam reflected off an etched portion of the wafer is measured and compared to a predetermined phase shift that corresponds to the desired etch depth. Unfortunately, the above discussed optical emission spectroscopy and other monitoring and measuring systems are plagued by inadequate signal to noise ratios to achieve in-situ or real time data processing, as well as the minimum etch depth being limited by the wavelength of the light source used in the monitor. Also, the film thickness or film thickness change is typically measured at a fixed spot, such as a fixed spot on a wafer. Disadvantageously, the overall film thickness across the wafer is unknown as only the thickness at that measured spot is determined, thus leading to an increased risk of detecting film thickness from the incorrect location where features of the film thickness may not be representative for the entire wafer. Furthermore, these systems often have the disadvantage of requiring substantial modification of the conventional equipment and processes thereby making them undesirable, expensive, time consuming, difficult to integrate, inefficient and impracticable.
Accordingly, a need continues to exist in the art for low cost improved systems and methods for accurately and directly measuring, monitoring and controlling film deposition thickness across the entire wafer surface within a deposition tool whereby the deposited material is uniform from wafer to wafer.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an improved low-cost method and system for direct, real-time measurement of thickness of deposited film during the deposition process.
Another object of the present invention is to provide a method and a system for real-time, in-situ wafer fabrication processes that prevents misprocessing errors, corrects for process drifts and detection of incorrect tool operation by real-time detection of deposited film thickness during wafer processing by detecting unusual signal behaviors of the system hardware or processing problems that would negatively affect the film measurement.
It is another object of the present invention to provide a method and a system for real-time, in-situ wafer fabrication processes that significantly reduce the wafer reworking.
Yet another object of the present invention is to provide a method and a system for real-time, in-situ wafer fabrication processes that drastically reduce processing costs, processing time and wafer waste.
Still another object of the present invention is to provide a method and a system for a real-time, in-situ wafer fabrication process whereby the deposition process may be stopped at an exact moment when the deposited film has reached a desired thickness.
Yet another object of the invention is to provide a method and a system for real-time, in-situ wafer fabrication processes that actively, in real-time, recognize the type wafer for depositing the desired film and film thickness thereon a surface of such wafer.
A further object of the invention is to provide a method and a system for real-time, in-situ wafer fabrication processes including processing tools having low costs and simplicity of such tools associated therewith.
Another object of the present invention is to provide a method and a system for a real-time, in-situ wafer fabrication process that obviates the need for human control for better automation.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects, which will be apparent to those skilled in art, are achieved in the present invention which is directed to, in a first aspect, a method for measuring film thickness on a substrate in a processing chamber both in real-time and in-situ. The method includes providing a processing chamber having roughened internal surfaces and emitting a radiation within the processing chamber whereby the radiation is directed toward and contacts a wafer surface having a film being processed thereon. The radiation is reflected off the wafer surface and directing toward and contacts the roughened internal surfaces. The radiation then diffusely reflects off the roughened internal surfaces and is collected to measure a thickness of the film being processed thereon the wafer surface. The roughened internal surfaces may have a variety of shapes including dome-shaped, hemispherical, cylindrical, oval, square, cylindrical square, cylindrical parabolic and combinations thereof.
In the invention, the processing chamber may comprise a material having a naturally occurring surface roughness to provide the roughened internal surfaces. Alternatively, the roughened internal surfaces may be provided by a method including grinding, polishing, sand blasting, etching, and machining the internal surfaces of the processing chamber. Still further, the roughened internal surfaces may be provided by conformally coating internal surfaces of the processing chamber with a material having a naturally occurring roughness.
The at least one optical view port may be provided at any location along a perimeter of the processing chamber for collecting the radiation diffusely reflected off the roughened internal surfaces to measure the thickness of the film. The optical view port has roughened internal surfaces to randomize directionality of incident radiation resulting in diffusely reflected radiation. In accordance with the invention, the at least one optical view port may comprise a window retracted into a small opening located at any location along the perimeter of the processing chamber. Alternatively, the at least one optical view port may include a fine metal mesh screen over an internal surface of the at least one optical view port to prevent deposition of the film thereon the internal surface of the at least one optical view port.
In the first aspect, the film being processed may include depositing a film thereon the wafer surface, or alternatively, etching a deposited film thereon the wafer surface. The radiation may be emitted from a plasma generated within the processing chamber, or alternatively, the radiation may be emitted into the processing chamber from an external radiation source.
In a second aspect, the invention discloses a method for measuring a deposited film thickness on a substrate in a deposition chamber both in real-time and in-situ. The method includes providing a processing chamber having roughened internal surfaces, at least one optical view port at any location along a perimeter of the processing chamber and a radiation source. A radiation is emitted within the processing chamber from the radiation source whereby the radiation is directed toward and contacts a wafer surface having a film being deposited thereon. The radiation is reflected off the wafer surface and directing toward and contacts the roughened internal surfaces. The radiation then diffusely reflects off the roughened internal surfaces and is collected using the at least one optical view port. A thickness of the film across the wafer surface is then analyzed based on the collected diffuse radiation. The processing chamber may comprise a deposition tool including a physical vapor deposition, a chemical vapor deposition, a plasma enhanced chemical vapor deposition and a high density plasma deposition. The processing chamber may also comprise a plasma etching or plasma cleaning tool.
In the second aspect, the degree of roughness average of the roughened internal surfaces at least equals a wavelength of the deposited film. The at least one optical view port may be located below the wafer surface for collecting the diffusely reflected radiation. Further, the at least one optical view port may comprise a material including sapphire, alpha-alumina and yttrium aluminum garnet. Optionally, the second aspect may further include a plurality of optical view ports located at a variety of locations along the perimeter of the processing chamber both above and below the wafer surface.
In accordance with the invention, the radiation source may comprise a plasma generated within the processing chamber including, for example, helium, neon, argon, krypton, xenon, oxygen, fluorine, nitrogen, nitrogen monoxide, carbon monoxide, chlorine, bromine, hydrogen and silicon, or ions thereof. Alternatively, the radiation source may comprise an external radiation source emitting radiation into the processing chamber including, for example, ultra violet, visible, X-Ray and near infrared radiation source. The deposited film may include, for example, silicon oxide, fluorinated silicon oxide, phosphorus doped silicon oxide, boron doped silicon oxide, diamond-like carbon, polymers, silicon nitride, titanium nitride, tantalum nitride and carbon nitride deposited to a thickness ranging from about 50 xc3x85 to about 20,000 xc3x85. The collected diffuse radiation may have a wavelength ranging from about 0.1 nm to about 5000 nm. The thickness of the film across the wafer surface is analyzed by calculating, in parallel, a plurality of wavelengths from a plurality of emissions reflecting off the wafer surface and diffusely reflecting off the roughened internal surfaces.
In a third aspect, the instant invention is directed to a processing chamber for measuring film thickness on a substrate in real-time and in-situ. The processing chamber includes a chamber body with roughened internal surfaces, at least one optical view port located at any location along a perimeter of the chamber body and a radiation source. In the processing chamber the radiation is emitted from the radiation source, reflected off a wafer surface and secondarily and diffusely reflected off the roughened internal surfaces of the chamber body whereby the diffusely reflected radiation is collected by the at least one optical view port to measure a thickness of a film across the wafer surface. The radiation source may comprise a plasma generated within the chamber body, or alternatively, an external radiation source emitting radiation into the chamber body.
In accordance with the third aspect, the roughened internal surfaces of the chamber body may be dome-shaped, hemispherical, cylindrical, oval, square, cylindrical square, cylindrical parabolic and combinations thereof. The chamber body may comprise a material having a naturally occurring surface roughness to provide the roughened internal surfaces, or alternatively, the roughened internal surfaces may comprise a material having a naturally occurring surface roughness conformally coating on internal surfaces of the chamber body.
The at least one optical view port may have roughened internal surfaces to randomize directionality of incident and the diffusely reflected radiation, or alternatively, may comprise a window retracted into a small opening located at any location along the perimeter of the chamber body. The optical view port may further include a fine metal mesh screen over an internal surface thereof to prevent deposition of the film on an internal surface of the view port. Optionally, a plurality of optical view ports may be provided whereby they are located at a variety of locations along the perimeter of the chamber body, both above and below the wafer surface.